1. Field
One or more embodiments relate to a laminated electrolyte membrane, a method of preparing the same, a membrane electrode assembly including the laminated electrolyte membrane, and a fuel cell including the membrane electrode assembly.
2. Description of the Related Art
Fuel cell systems that are operated at a temperature of 100° C., or more, in a non-humidified environment, can include an electrolyte membrane prepared by impregnating a basic structural polymer with an acid, as described in (Japanese Patent Application Laid-open No. hei 11-503262. As an example of the electrolyte membrane described above, an electrolyte membrane prepared by impregnating a polybenzimidazole film with sulphuric acid or phosphoric acid is disclosed in the art. Fuel cells using such electrolyte membranes effectively use generated heat, thereby having a higher energy efficiency than fuel cells that use an electrolyte membrane comprising a fluoropolymer, such as Nafion (Dupont Co.) that are operated at relatively lower temperatures of 80° C., or less.
However, in fuel cells using an acid-impregnated basic polymer membrane, acid leaks out of the electrolyte membrane during operation, and thus, the performance of the fuel cells deteriorates and the leaked acid can corrode adjacent elements. To address these problems, a method of reducing acid leakage from an electrolyte membrane, wherein the impregnated acid is polymerized in an electrolyte, to prepare an acidic polymer, is disclosed in Japanese Patent Application Laid-open No. hei 2005-527073.
However, according to Japanese Patent Application Laid-open No. hei 2005-527073, if an electrolyte membrane has defects therein, such as pin holes, the performance of a fuel cell including the electrolyte membrane is significantly reduced by the defective electrolyte membrane, rather than by the leakage of acid, and the fuel cell cannot be operated efficiently.